On the day the Afghan President was supposed to hand over power to a United Nations-sponsored caretaker government, Burhanuddin Rabbani was otherwise engaged. His troops were digging foxholes and strengthening the capital's defences against attack by a militia of Islamic students.

Mr Rabbani's excuse for not quitting the presidency yesterday is that the emergence of the Koranic students as a powerful force in Afghanistan - in two months they have swept through nine provinces - makes the UN's interim council worthless. The student militia, known as the Taliban, refuse to join the proposed council. The students accuse those proposed council members who belong to the mujahedin factions of betraying Islam for killing so many Afghans with their feuds.

Another compelling reason Mr Rabbani stalls is that the students have done his government a huge service. The Taliban, many of whom fought for more than a decade against the Russian occupation and know the workings of a rocket-propelled grenade nearly as well as the Koran, defeated Mr Rabbani's arch-enemy, Gulbuddin Hekmatyar.

Coming in from Mr Hekmatyar's exposed southern flank, the militia scattered his Hezbi-Islami forces from the around Kabul, from where they had poured thousands of rockets into the capital, killing tens of thousands over the past two years.

With his enemy in retreat, Mr Rabbani has moved up his troops, securing Kabul. The Taliban are within eight miles of the city, but if Mr Rabbani chooses to halt their advance, as it seems, the students would face punishing losses. Mr Rabbani is also said to be wary of the Taliban; some of his officials suspect them of having support from fundamentalist groups in Pakistan. The Taliban are also mostly Pathans, while Mr Rabbani and his Kabul defenders are Tajiks - the two clans have long been adversaries.

Meanwhile, the UN's proposed caretaker council is unravelling. Several mujahedin factions are backing out, and the UN's Tunisian envoy, Mahmoud Mestiri, may have no choice but to abandon his mission.

Many Kabul citizens consider the Taliban heroes. Not only did they liberate the city from rocket-fire, but the students also opened roads into the city. The cold, starving Kabul residents can now buy oranges, meat and kerosene. One young woman, Firozan, her hair veiled under a smart scarf in the Islamic fashion, said: "We've heard that the Taliban have brought peace to the towns under their control. They say they are good Muslims, so hopefully they won't start shelling Kabul they way the other mujahedin did.''

The Taliban conquer by offering peace. Their leader is a cleric named Haji Mohammed Omar from the southern city of Kandahar who supposedly received a vision from Allah telling him to raise a new Islamic army.

One follower, Wali Mohammed, said: "He started with 20 students; now he has 20,000 Taliban." They control most of southern Afghanistan.

A senior commander, Mohammed Rabbani, said: "We don't believe in heavy artillery and weapons. It is only thanks to Allah that we've been able to defeat so many strong armies in Afghanistan."

The Taliban's method is simple but lethal. One foreign aid worker explained: "They send word up to whatever commander stands in their way that they're coming: `If you are an honest Muslim you will join us, if not, you'll be swinging from a tree come tomorrow.' It's amazing how few mujahedin stayed to fight them. Nearly all ran."

The students claim they do not want to run the country. Their only aim, they insist, is to disarm all the feuding warlords, and Mr Rabbani is highest on their list. A force of 2,000 militia stands just beyond the southern hills surrounding Kabul. "We want to collect the weapons of all the militiamen in Kabul. We don't want to fight; we'll do it through negotiations."

Preachers and students have begun to stream into Kabul, urging Mr Rabbani's defenders to give up their guns. After so many years of fighting this message of peace may prove Mr Rabbani's downfall.